1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor substrate wherein an epitaxial film is grown in the inside of a trench and thereby the inside of the trench is filled with the epitaxial film.
2. Description of the Related Art
Japanese Examined Patent Application Publication No. 3485081 discloses a method for manufacturing a semiconductor substrate wherein an epitaxial film is filled in a trench and thereby a diffusion layer of a high aspect ratio is formed. Japanese Unexamined Patent Application Publication No. 2003-124464 discloses in a vertical type MOS transistor, a drift domain is made into a super junction structure (P/N column structure) and proposes a method of manufacturing a semiconductor substrate wherein an epitaxial film is filled in a trench and thereby a diffusion layer is formed.
However, when a void is generated in an epitaxial film filled in a trench, the problem arises that a breakdown occurs in the upper portion of the void and the withstand pressure decreases. Thus, the generation of the void in a filled epitaxial film deteriorates performance of the element. Specifically, it causes the decline of the withstand pressure of the above-mentioned super junction structure (P/N column structure), or the decline of the withstand pressure junction leak yield accompanying the generation of a crystal defect arising from a void, or a resist left in the portion of the void in the trench which leads to contamination in the process, or the like.